What is an Array?
An array is a data type in typescript wherein you can store multiple values. Let’s learn how to declare and assign values for an array.
Since typescript is a strongly typed language, you have to tell what will be the data type of the values in an array. Otherwise, it will consider it as of type any.
Declare and Initialize an Array
Syntax:
let nameofthearray : Array<typehere>
Example
let months: Array<string> = ["Jan", "Feb", "March", "April", "May", "June", "July", "Aug", "Sept", "Oct", "Nov", "Dec"]; //array with all string values.
let years: Array<number> = [2015, 2016, 2017, 2018, 2019]; //array will all numbers
let month_year: Array<string | number> = ["Jan", 2015, "Feb", 2016]; //array with string and numbers mixed.
let alltypes: Array<any> = [true, false, "Harry", 2000, { "a": "50", "b": "20" }]; //array of all types boolean, string , number , object etc.
Different Ways to access elements from an Array
To get the elements from an array, the values starts from index 0 to the length of the array.
Example:
let years: Array<number> = [ 2016, 2017, 2018, 2019]; //array will all numbers years[0]; // output will be 2016 years[1]; // output will be 2017 years[2]; // output will be 2018 years[3]; // output will be 2019
You can also get the elements from an array using for loop as shown below:
Using for loop
let years: Array<number> = [ 2016, 2017, 2018, 2019];
for (let i=0;i<=years.length; i++) {
console.log(years[i]);
}
Output:
2016
2017
2018
2019
Using for-in loop
let years: Array<number> = [ 2016, 2017, 2018, 2019];
for (let i in years) {
console.log(years[i])
}
Output:
2016
2017
2018
2019
Using for-of loop
let years: Array<number> = [ 2016, 2017, 2018, 2019];
for (let i of years) {
console.log(i)
}
Output:
2016
2017
2018
2019
Using foreach loop
let years: Array<number> = [ 2016, 2017, 2018, 2019];
years.forEach(function(yrs, i) {
console.log(yrs);
});
Output:
2016
2017
2018
2019
Typescript Array Methods
Typescript Array object has many properties and methods which help developers to handle arrays easily and efficiently. You can get the value of a property by specifying arrayname.property and the output of a method by specifying array name.method().
length property
=> If you want to know the number of elements in an array, you can use the length property.
Reverse method
=> You can reverse the order of items in an array using a reverse method.
Sort method
=> You can sort the items in an array using sort method.
Pop method
=> You can remove the last item of an array using a pop method.
Shift method
=> You can remove the first item of an array using shift method.
Push method
=> You can add value as the last item of the array.
concat method
=> You can join two arrays into one array element.
Example for length property
let months: Array<string> = ["Jan", "Feb", "March", "April", "May", "June", "July", "Aug", "Sept", "Oct", "Nov", "Dec"]; //array with all string values. console.log(months.length); // 12
Example for reverse method:
let months: Array<string> = ["Jan", "Feb", "March", "April", "May", "June", "July", "Aug", "Sept", "Oct", "Nov", "Dec"]; //array with all string values. console.log(months.reverse()); // ["Dec", "Nov", "Oct", "Sept", "Aug", "July", "June", "May", "April", "March", "Feb", "Jan"]
Example for sort method:
let months: Array<string> = ["Jan", "Feb", "March", "April", "May", "June", "July", "Aug", "Sept", "Oct", "Nov", "Dec"]; //array with all string values. console.log(months.sort()); // ["April", "Aug", "Dec", "Feb", "Jan", "July", "June", "March", "May", "Nov", "Oct", "Sept"]
Example for pop method:
let months: Array<string> = ["Jan", "Feb", "March", "April", "May", "June", "July", "Aug", "Sept", "Oct", "Nov", "Dec"]; //array with all string values. console.log(months.pop()); //Dec
Example for shift method:
let months: Array<string> = ["Jan", "Feb", "March", "April", "May", "June", "July", "Aug", "Sept", "Oct", "Nov", "Dec"]; //array with all string values. console.log(months.shift()); // Jan
Example for push method:
let years: Array<number> = [2015, 2016, 2017, 2018, 2019]; //array will all numbers
console.log(years.push(2020));
years.forEach(function(yrs, i) {
console.log(yrs); // 2015 , 2016,2017, 2018, 2019,2020
});
Example for concat method:
let array1: Array<number> = [10, 20, 30]; let array2: Array<number> = [100, 200, 300]; console.log(array1.concat(array2)); //[10, 20, 30, 100, 200, 300]
About Author
